A user equipment-to-user equipment proximity service (ProSe) or Device to Device Proximity Service (D2D ProSe) technology can implement direct communication between user equipments and produce a corresponding communication service.
In an existing mobile communications system that supports the D2D ProSe technology, a user equipment that supports a ProSe needs to let, in a manner of sending a discovery signal, another user equipment sense existence of the ProSe user equipment, so that the another user equipment may establish direct communication with the ProSe user equipment according to the discovery signal.
When the mobile communications system that supports the D2D ProSe technology is applied to intra-frequency micro cells or a multi-carrier cell, because a process of establishing direct communication depends on reception of a discovery signal of a ProSe user equipment, when a certain ProSe user equipment cannot receive the discovery signal of the ProSe user equipment due to signal interference or another reason, the ProSe user equipment cannot sense the existence of the ProSe user equipment, and therefore cannot establish direct communication with the ProSe user equipment.